An Introduction to Ray Tracing
TL;DR — The standard ray-tracing text, released free after rights reverted from Elsevier in 2019.
⬇ Download the archived copy — kept here so the document survives its source going dark. Explicitly free / author-released / CC.
Version 1.2, 28 January 2019 — “made available free of charge thanks to the generosity of the authors and Academic Press (now Elsevier). Rights for this book were reverted to the editor, Andrew Glassner, by Elsevier, in 2019.”
351 pages, the canonical treatment of ray tracing from the era in which the algorithms were settled, contributed by the people who settled them.
The rights story is half the reason it belongs here: an out-of-print standard reference that became free because its editor asked for it back.
Where this came from
351 pages. A copy is archived locally against link rot; the header links the original source.